Symptoms

Dialog 1: Soft block in Windows Server 2008 DCPROMO warning against the creation of new domains with single-label DNS names:

Title: Active Directory Domain Services Installation Wizard

Text:

The DNS name "<single label DNS domain name> proposed for this Active Directory domain consists of a single label, which is not recommended. DNS domain name should be unique and fully qualified, consisting of one or more labels separated by a period ("."), followed by a top level domain.

Example: corp.<domain>.com

If you click No, you can assign a fully qualified DNS name like the example. If you implement a single-label DNS domain name, you must configure all member computers and domain controllers as described in article 300684 in the Microsoft Knowledge Base (http://go.microsoft.com/fwlink/?LinkId=92467) so they can register records and resolve queries until the domain is retired.

Do you really want to assign a single-label DNS domain name to this Active Directory domain?

The DNS name "<single-label domain>" proposed for this Active Directory domain consists of a single label. DNS domain names should be unique and fully qualified, consisting of one or more labels separated by a period ("."), followed by a top-level domain.

Some Microsoft products may continue to function with single-label domains and other namespace configurations, however, they are not a recommended configuration for future deployments. Microsoft recommends that customers deploy infrastructure using common, tested configurations to minimize extra deployment and testing costs.

Microsoft will continue to provide customers with existing single-label domain configurations with best-effort support, such that Microsoft remains committed to triaging and evaluating any technical issues that customers experience. For more information, see the following article in the Microsoft Knowledge Base:

Resolution

The best practice is to create Active Directory forest root domains with fully qualified DNS names that consist of two or more name parts separated by a period (i.e. contoso.com, corp.contoso.com or contoso.<two letter country code top-level domain> vs. the single-label name contoso. )

If you are impacted by Microsoft applications and Microsoft operating system components experiencing deployment or operational problems caused by the use of single-label domains you should open support incidents in an attempt to resolve those issues.

Application support for single-label domains exists on a case-by-case basis. Contact your application developer for a statement of support. For more information about product compatibility with SLDs, see the Microsoft DNS Namespace Planning Solution Center.

For more information about Active Directory and single-label DNS names, see the following article in the Microsoft Knowledge Base: